JP6302165B2 - Image projection system - Google Patents

Description

  The present invention relates to a technique for preventing information leakage to non-users when providing information to a user using a screen and a projector.

  With the recent development of information communication networks, various types of information such as images and texts can be received by portable communication devices. Thereby, for example, a service provider such as an emergency coordinator who rushes to a security contractor or a nurse who visits a hospital room can check information related to the security contractor and the patient at the service provider. .

  Conventionally, as in the invention described in Patent Document 1 below, wearable imaging in which information related to a contractor or a patient is projected onto a service provider's hand or the like by a portable projector attached to the body of the service provider A device has been proposed. As a result, the service provider can smoothly execute the business while confirming necessary information without holding the communication device.

JP-T-2006-502444

  However, the information to be projected may include confidential information such as a security contractor's or patient's privacy information and a trade secret, and it is desirable to keep confidentiality as high as possible. For this reason, it is not desirable that such information be projected in a state that can be visually recognized by anyone other than the service provider. For example, if the nurse moves his / her palm while projecting information related to the patient onto the palm of the nurse, inadvertent projection onto a wall or floor occurs. As a result, there is a problem that there is a high risk that information that should not be shown to other than the nurse will be shown to surrounding patients.

  Therefore, an object of the present invention is to provide an image projection system, a screen, and a projector that can prevent information leakage to anyone other than a service provider even if information is accidentally projected onto a wall or floor.

The present invention is an image projection system including a projector and a screen, and a storage unit that stores a noise image determined according to a predetermined rule, and an image generation that generates a concealed image by subtracting the noise image from a presentation information image And a projection unit that projects the concealed image onto a screen on which the noise image is formed, and the presentation information image is restored on the screen by the projection.

  In one embodiment of the image projection system according to the present invention, the image generation unit sets a pixel value so that a pixel value of the presentation information image is higher than a pixel value of the noise image.

  In another embodiment of the image projection system according to the present invention, the screen is a glove, and the projector is a projector that can be worn on a user's body.

  According to the image projection system, the screen, and the projector of the present invention, even if highly confidential information is inadvertently projected, it can be made difficult to be viewed by anyone other than the service provider with the right to view.

It is explanatory drawing of the image of embodiment. It is explanatory drawing of the image of embodiment. It is usage explanatory drawing of embodiment. It is usage explanatory drawing of embodiment. It is a block diagram of embodiment. It is an operation | movement flowchart of embodiment. It is an operation | movement flowchart of embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, this embodiment will be described with reference to FIGS. 1 and 2.

  An example in which a grayscale image is used as the presentation information image 10 will be described. Note that “pixel value” in the following description means a luminance value. Therefore, the higher the pixel value of the image projected from the projector, the brighter the projected image.

  FIG. 1 is a diagram showing an example of an image used in the present embodiment and its operation.

  In the presentation information image 10, information (presentation information) presented to a service provider such as an emergency coordinator who rushes to a security contractor or a nurse who visits a hospital room is text or graphics (privacy information, trade secret, etc.) This is an image expressed with high confidentiality information. The presentation information image 10 is expressed in a state where characters and images of the presentation information are visible to non-users. Here, the presentation information image 10 may be generated by performing normalization that narrows the pixel value range in order to secure a decrease in luminance due to the concealment process 12. Details of normalization will be described later.

  The noise image 11 is an image that makes it difficult for a human to visually recognize the presentation information (characters and graphics) included in the presentation information image 10 by being combined with the presentation information image 10. Therefore, the noise image 11 is generated in advance according to a predetermined rule for making it difficult for humans to visually recognize the presentation information. Specifically, the noise image 11 matches the pixel information with the presentation information image 10 and takes into account the confidentiality of the presentation information after synthesis and the restoration of presentation information by the color adding action 14 described later. Are determined by random numbers in the range of 0 to 220. The noise image 11 is previously formed on the screen by printing or the like. Details of the method of generating the noise image 11 will be described later.

  The concealment process 12 is a process for synthesizing the presentation information image 10 and the noise image 11. Specifically, this is image processing for subtracting the pixel value of the pixel corresponding to the pixel in the noise image 11 from the pixel value of each pixel constituting the presentation information image 10.

  The concealed image 13 is an image in which the presentation information generated from the presentation information image 10 and the noise image 11 by the concealment process 12 is not visible. This hidden image 13 is projected by the projector 1. Each pixel value of the presentation information image 10 is randomized by the noise image 11, and even if the concealed image 13 is projected onto the wall or floor, humans cannot visually recognize the presentation information or it is very difficult to visually recognize the presentation information. That is, the presentation information image 10 is represented in a state where characters and images of the presentation information are not visible to users and non-users.

  The color adding action 14 occurs between the noise image 11 formed on the screen and the concealed image 13 projected on the screen. This color adding action 14 can be regarded as an inverse process of the concealment process 12. By this color adding action 14, the presentation information image 10 is restored from the concealed image 13, and the characters and figures of the presentation information represented in the presentation information image 10 can be visually recognized by humans.

  Specifically, on the screen on which the noise image 11 is formed, each pixel of the noise image 11 is exposed to ambient light, so that reflected light corresponding to each pixel value is projected according to each pixel value of the hidden image 13. Light is added, and the intensity (brightness) of reflected light from the screen changes. When the projection position of the concealment image 13 matches the formation position of the noise image 11 on the screen using this change in intensity, the image processing effect of the concealment process 12 performed on the concealment image 13 at the corresponding pixel position is negated. Thus, the presentation information image 10 is restored. Therefore, the concealment process 12 can be rephrased as an encryption process, and the color adding action 14 as a decryption process.

  When the projection position of the concealed image 13 is not the noise image 11 on the screen but a wall or floor where the noise image 11 is not formed, the color adding action 14 does not occur and the presentation information image 10 is not restored. For this reason, persons other than the user who cannot see the concealed image 13 projected on the screen cannot visually recognize the characters and graphics of the presentation information.

  The projected image 15 is an image in which the presentation information image 10 is restored from the concealed image 13 by the additive action 14. That is, the projected image 15 is an image in which characters and graphics of the presentation information can be visually recognized by humans.

  FIG. 2 is a diagram showing changes in pixel values due to the concealment process 12 and the additive action 14. In FIG. 2, pixel values of x coordinates 1, 2, 3, and 4 at a certain y coordinate (for example, y = 3) of the image (pixel values of a thick line portion in FIG. 2A) are shown as an example.

  FIG. 2B shows the pixel value range Lr of the presentation information image 10, and FIG. 2C shows the pixel value range Lo of the noise image 11.

  Each pixel value of the noise image 11 is randomly determined in the range of [Lo_min, Lo_max]. The wider the range of pixel values of the noise image 11, the greater the color reduction width, and the greater the degree of concealment of the concealed image 13. Therefore, the pixel value range of the noise image 11 should be as wide as possible.

  On the other hand, if the pixel value range of the noise image 11 is too wide, the contrast of the projection image 15 restored by the additive action 14 becomes low and it becomes difficult to visually recognize. Specifically, in order to realize the restoration by the additive action 14, it is necessary to increase the minimum pixel value Lr_min of the presentation information image 10 by the extent that the pixel value range of the noise image 11 is expanded. However, the upper limit of the maximum pixel value Lr_max of the presentation information image 10 is 255, and the contrast of the presentation information image 10 decreases as Lr_min increases. For this reason, the contrast of the projected image 15 becomes low.

  Therefore, it is necessary to set Lo_min and Lo_max that are balanced in advance. For example, when the range of pixel values that can be projected by the projection unit is [0, 255], Lo_min can be 0 and Lo_max can be 220. FIG. 2C shows an example in which the pixel values of the x coordinates 0, 1, 2, and 3 in the noise image 11 are determined as 102, 29, 146, and 180, respectively.

Next, normalization of the presentation information image 10 will be described in detail.
Each pixel value of the presentation information image 10 is normalized so as to be within the range of [Lr_min, Lr_max]. Lr_min is set to a value larger than 0 so that the luminance decreases due to subtractive color, that is, each pixel value of the presentation information image 10 is set to be higher than the corresponding pixel value of the noise image 11, and (Lr_max−Lr_min ) Is preferably set as large as possible so as to increase the contrast of the projected image. The reason why Lr_min is set to a value larger than 0 is that even if the concealment process is performed, the pixel value of 0 remains 0 and the concealment of the generated concealed image 13 is reduced. If Lr_min ≧ Lo_max, the presentation information image 10 can be completely restored in the projection image 15. However, as Lr_min is increased, the contrast of the projection image 15 is lowered, and it becomes difficult to visually recognize characters and figures of the presentation information.

  Therefore, Lr_min is set to be smaller than Lo_max to prevent a decrease in contrast. As a result, the restoration of the presentation information image 10 is not complete, but the positions of the pixels whose restoration is incomplete are scattered at random, so that a reduction in the visibility of the presentation information can be suppressed. For example, in the above example where Lo_min is 0 and Lo_max is 220, Lr_min can be 128 and Lr_max can be 255 as shown in FIG.

Assuming that the pixel value of the presentation information image 10 before normalization is L_min ≦ L (x, y) ≦ L_max and the pixel value of the presentation information image 10 after normalization is Lr (x, y), normalization follows the following equation. Do.
Lr (x, y) = (L (x, y) -L_min) / (Lr_max-Lr_min) / (L_max-L_min) + Lr_min (1)

  FIG. 2B shows an example in which the pixel values 255, 0, 255, 0 of the presentation information image 10 corresponding to the noise image 11 are normalized to 255, 128, 255, 128.

Next, generation of the hidden image 13 will be described in detail.
If the pixel value of the presentation information image 10 is Lr (x, y) and the pixel value of the noise image 11 is Lo (x, y), the pixel value Ls (x, y) of the hidden image 13 is calculated by the following equation. The
Ls (x, y) = Lr (x, y) −Lo (x, y) (2)
However, Ls (x, y) = 0 when Lr (x, y) −Lo (x, y) <0

  FIG. 2D shows the pixel value Ls of the hidden image 13. FIG. 2D shows an example in which the pixel values of the hidden image 13 corresponding to the presentation information image 10 and the noise image 11 are calculated as 153, 99, 109, 0.

Next, the projection image 15 by the additive action 14 will be described in detail.
Assuming that the brightness of the projected concealed image 13 is Ls (x, y) and the brightness of each pixel in the noise image 11 formed on the screen is Lo (x, y), the brightness Lp ( x, y) follows the following formula.
Lp (x, y) = Ls (x, y) + Lo (x, y) (3)

  FIG. 2E shows the pixel value Lp of the projection image 15. FIG. 2E illustrates luminances 255, 128, 255, and 180 of the projection image 15 obtained by adding the noise image 11 and the concealment image 13 to each other.

  The example in which the presentation information image 10 and the noise image 11 are gray images has been described above. However, these images may be color images. In this case, the luminance value of each color component is determined for each pixel based on a random number to generate the noise image 11, and the concealment process is performed on each color component for each pixel of the presentation information image 10 to generate the concealed image 13. Good.

Next, the system configuration of this embodiment will be described.
FIG. 3 and FIG. 4 show usage examples of a system including a screen and a projector according to the present embodiment.

  In the following, a case where presentation information is transmitted to an emergency response person (service provider) rushing to a security contractor will be described as an example.

  As shown in FIG. 3 (a), the emergency agent 4 wears the projector 1 on the chest, the glove-type screen 2 on the hand, and the portable communication terminal 3 on the chest pocket. As shown in FIG. 3B, the screen 2 is printed with an ID number 40 for identifying the noise image 11 and the type of the noise image 11. When the emergency responder 4 confirms the presentation information, as shown in FIG. 4A, the concealed image 13 is transmitted from the mobile communication terminal 3 to the projector 1, and the projector 1 projects the concealed image 13, The projection light is matched with the noise image 11 printed on the glove-type screen 2. Then, as shown in FIG.4 (b), the projection image 15 is displayed and the emergency response staff 4 can confirm presentation information. When the projection light is not matched with the noise image 11, that is, when the projection light is projected onto the floor or wall, the concealed image 13 is projected, and thus the human cannot visually recognize the presentation information.

  The projector 1 is a small projector that can be carried by the emergency responder 4 while wearing it in a breast pocket or a shoulder. The projector 1 is connected to the mobile communication terminal 3 via a short-range wireless communication network such as Bluetooth or a wired communication network such as USB. Then, the hidden image 13 received from the mobile communication terminal 3 is projected.

  The screen 2 is a screen on which the noise image 11 is formed in advance by printing or the like. The screen 2 may be a screen on which the noise image 11 is formed and the image projected from the projector can be projected. In the embodiment, the glove held by the emergency responder is described as the screen 2, but a predetermined document or notebook sandwiched between binders may be used. Moreover, the screen 2 which displays an image not only by printing but by light may be used. For example, even when the screen 2 is an electronic paper or a liquid crystal display and the noise image 11 is displayed on the screen, the color adding action 14 can be realized.

  A plurality of noise images 11 are prepared, and the screen 2 is managed so as to be identifiable by an ID number 40 for identifying the noise image 11. For example, the emergency responder 4 has a plurality of glove-type screens 2, and a noise image 11 and a corresponding ID number 40 that are different for each glove are printed. Here, the plurality of noise images 11 are prepared in order to reduce the risk when the screen 2 is lost. When different noise images 11 are formed on the screen 2, the noise images 11 are allowed to overlap if the number of the noise images 11 is increased sufficiently, for example, 1000 types. Since the screen 2 is not easily available as a commercial product, it is effective in preventing leakage of presentation information to a malicious person. By preparing a plurality of types of noise images 11 and changing the noise image 11 used for generating the concealment image 13 each time, the effect of preventing leakage is further enhanced. Further, by managing by the ID number, even if the screen 2 is lost, the noise image 11 corresponding to the ID number of the lost screen 2 is not used for the generation of the concealment image 13 thereafter, The effect of preventing leakage is further enhanced.

  The mobile communication terminal 3 is a communication terminal device that can be carried by a counselor, such as a smartphone or a mobile phone. Multiple emergency responders are carrying each. Presentation information is received from an information server (not shown) installed in a security center or the like via a communication network such as the Internet or a public telephone line, a presentation information image 10 is generated from the presentation information, and a concealed image 13 is generated from the presentation information image 10. Is transmitted to the projector 1. Alternatively, the presentation information image 10 may be generated, and a process of narrowing and normalizing the pixel value range of the image may be performed.

  The presentation information is, for example, the address of the contractor in which the monitoring abnormality has occurred, the contractor name, the building drawing, the character or graphic representing the type of the monitoring abnormality, the character or graphic representing the sensor that has detected the monitoring abnormality, or the like.

  In the present embodiment, the projector 1 and the mobile communication terminal 3 are described as separate devices. However, the projector 1 may have the configuration of the mobile communication terminal 3.

  In the present embodiment, an example in which the mobile communication terminal 3 generates the presentation information image 10 and normalizes the presentation information image 10 is described. However, the mobile communication terminal 3 generates the presentation information image 10 in advance (for example, a monitoring center). The mobile communication terminal 3 may receive the presentation information image 10 and the standardized presentation information image 10. Further, the hidden image 13 may be received in advance (for example, a monitoring center). In this case, necessary configurations such as a presentation information image generation unit 310 and a concealed image generation unit 311 to be described later may be provided outside as an image generation unit of the present invention to receive the generated information.

  FIG. 5 is a diagram illustrating the configuration of the projector 1 and the mobile communication terminal 3.

  The mobile communication terminal 3 includes an external input I / F 30, an image output unit 32, an operation input unit 33, and a storage unit 34, which are connected to the control unit 31.

  The external input I / F 30 is an interface that inputs presentation information from an external device to the control unit 31. For example, it comprises a communication interface circuit that wirelessly connects the mobile communication terminal 3 to a wide area communication network.

  The control unit 31 is an arithmetic device such as a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or an MCU (Micro Control Unit). The program describing the operations of the presentation information image generating unit 310, the concealed image generating unit 311, the noise image setting unit 312 and the like is read from the storage unit 34 and executed, thereby functioning as these units. In the present embodiment, the control unit 31 is the image generation unit of the present invention.

  The image output unit 32 is an interface that outputs the concealed image 13 generated by the control unit 31 to the projector 1. For example, the communication interface circuit is configured to wirelessly connect the mobile communication terminal 3 to a near field communication network.

  The operation input unit 33 is an interface for inputting the ID number of the noise image 11 by the operation of the emergency response staff 4. For example, it is configured with a push button such as a numeric keypad or a touch panel, and the operation input information is output to the control unit 31.

  The storage unit 34 is a memory device such as a ROM (Read Only Memory) or a RAM (Random Access Memory). Various programs and various data are stored and input / output from / to the control unit 31. Various data includes a noise image 11. A plurality of noise images 11 are stored in advance in association with the ID number 40.

  The presentation information image generation unit 310 generates the presentation information image 10 from the presentation information input from the external input I / F 30 and outputs it to the hidden image generation unit 311. A predetermined layout process is applied to the characters and graphics of the presentation information to form an image. The presentation value image 10 is generated by normalizing the pixel value range by applying Expression (1) to each pixel of the presentation information that has been imaged. If the presentation information image 10 is bold, the randomness of the presentation information in the generated concealment image 13 may deteriorate. Therefore, the presentation information image generation unit 310 detects a thick line region in which a certain number of pixels having the same or similar pixel value continues from the presentation information image 10 for a certain number (for example, 10 pixels), and performs thinning processing on the region to provide the presentation information. The image 10 is corrected. Thereby, the randomness of the concealment image 13 is ensured more reliably, and the concealment fall of presentation information can be prevented.

  The concealed image generation unit 311 generates the concealment image 13 by combining the presentation information image 10 input from the presentation information image generation unit 310 and the noise image 11 stored in the storage unit 34, and supplies the concealment image 13 to the image output unit 32. Output. Specifically, according to the formula (2), the concealed image 13 is generated by subtracting the pixel value of the pixel corresponding to the pixel in the noise image 11 from the pixel value of each pixel constituting the presentation information image 10.

  Furthermore, the hidden image generating unit 311 can improve the confidentiality of the hidden image 13 by superimposing pseudo noise on the hidden image 13. Concerning the superimposition of pseudo noise, the hidden image generating means 311 compares the luminance difference between adjacent pixels in each pixel of the hidden image 13 with a predetermined similarity determination threshold value, and the adjacent luminance difference is smaller than the similarity determination threshold value. A similar pixel is detected, and a value based on a random number is added to the pixel value of the detected pixel. The similarity determination threshold value may be set to 5, for example, and the random number range may be set to 0 to 10, for example.

  The noise image setting unit 312 changes the noise image 11 used by the hidden image generation unit 311 among the noise images 11 stored in the storage unit 34. When the emergency response person 4 uses the operation input unit 33 to input the ID number 40 assigned to the screen 2 worn by himself / herself, the noise image setting unit 312 displays the noise image 11 corresponding to the ID number 40 as a concealed image. It is set as the noise image 11 used by the generation means 311. Further, the noise image setting unit 312 additionally writes in the storage unit 34 when update data including a new noise image 11 and its ID number is input from an external device. Further, the noise image setting unit 312 deletes the corresponding noise image 11 from the storage unit 34 when the ID number 40 of the noise image 11 is input together with the deletion instruction from the external device. In the present embodiment, an example in which a plurality of noise images 11 are stored in advance in the mobile communication terminal 3 has been described, but the ID number 40 input from the operation input unit 33 among the plurality of noise images 11 stored in the external device. The noise image 11 identified by (1) may be acquired by communication.

  The projector 1 includes an image input unit 110, a projection unit 112, a storage unit 113, and a projection stop switch 114, which are connected to the control unit 111.

  The image input unit 110 is an interface for inputting the concealed image 13 from the mobile communication terminal 3 to the control unit 111. For example, the projector 1 includes a communication interface circuit that wirelessly connects the projector 1 to a short-range communication network.

  The control unit 111 is an arithmetic device such as a CPU, DSP, or MCU. When the concealment image 13 is input from the image input unit 110, the control unit 111 stores the concealed image 13 in the storage unit 113 and outputs an operation start signal to the projection unit 112. Then, the hidden image 13 is output to the projection unit 112. When an operation of the projection stop switch 114 is detected while the projection unit 112 is operating, an operation stop signal is output to the projection unit 112. A program describing these operations and the like is read from the storage unit 113 and executed, thereby functioning as the control unit 111.

  The projection unit 112 includes optical components such as a light source and a mirror and a display element such as a DMD (Digital Micromirror Device) device. The hidden image 13 input from the control unit 111 is projected. It starts when an operation start signal is input from the control unit 111 and stops when an operation stop signal is input.

  The storage unit 113 is a memory device such as a ROM or a RAM. The storage unit 113 stores the hidden image 13 input from the image input unit 110. In addition, the storage unit 113 stores various programs and various data, and inputs and outputs them with the control unit 111.

  The projection stop switch 114 includes a button and a switch circuit. When the projection unit 112 is projecting the concealed image 13, the projection stop switch 114 is operated by the coordinator to instruct the projection stop.

Next, the operation of this embodiment will be described.
FIG. 6 is a flowchart showing the operation of the mobile communication terminal 3. Steps S10 to S19 are repeatedly executed in a predetermined cycle.

  First, the control unit 31 operates as the noise image setting unit 312 and confirms whether an instruction to select the noise image 11 is input from the operation input unit 33 together with the ID number 40 (S10). If it is input, the noise image setting unit 312 sets the noise image 11 corresponding to the ID number 40 from the noise images 11 stored in the storage unit 34 as the noise image 11 used for the concealment process 12 (S11). ). On the other hand, when there is no selection instruction input (NO in S10), step S11 is skipped.

  Next, the control unit 31 confirms whether or not the external input I / F 30 has received new presentation information from the external device (S12). If received (YES at S12), control unit 31 generates hidden image 13 (S13). If not received (NO in S12), control unit 31 skips steps S13 to S15.

  FIG. 7 is a detailed flowchart of the hidden image generation process in S13 of FIG.

  First, the control unit 31 operates as the presentation information image generation unit 310, and generates a presentation information image 10 by performing layout processing on the received presentation information (S31).

  The presentation information image generation unit 310 performs a thick line region detection process on the presentation information image 10 generated in step S31. When the thick line area is detected (YES in S32), the presentation information image generating unit 310 corrects the presentation information image 10 by performing a thinning process on the thick line area (S33). Thereby, the confidentiality of the confidential information displayed on the hidden image 13 is improved. On the other hand, when the thick line area is not detected (NO in S32), presentation information image generation means 310 skips step 33.

  Next, the presentation information image generation means 310 normalizes the expression (1) on the presentation information image 10 generated up to step S33 (S34).

  Next, the control unit 31 operates as the hidden image generation unit 311. The hidden image generation unit 311 reads the noise image 11 selected and instructed in step S10 of FIG. 6 from the storage unit 34, and subtracts the pixel value of the noise image 11 from the pixel value of the presentation information image 10 according to the equation (2). Then, the concealment image 13 is generated (S35). The hidden image generation unit 311 performs adjacent similar pixel detection processing on the hidden image 13 generated in step S35. That is, when an adjacent similar pixel is detected (YES in S36), pseudo noise is superimposed by generating a random value and adding it to the pixel value of the adjacent similar pixel (S37). On the other hand, when the adjacent similar pixels are not detected (NO in S36), hidden image generating means 311 skips step 37. When the process of FIG. 7 is finished, the control unit 31 advances the process to step S14 of FIG.

  Returning to FIG. 6 again, the hidden image generating means 311 outputs the hidden image 13 generated in step S13 to the image output unit 32, and the image output unit 32 sends the hidden image 13 to the projector 1 via the short-range communication network. Transmit (S14). The concealed image 13 may be stored in the storage unit 34, and the concealed image 13 in the storage unit 34 may be retransmitted to the projector 1 when a reprojection instruction is input from the operation input unit 33 by the coordinator. .

  Next, the control unit 31 deletes the presentation information and the presentation information image 10 from the storage unit 34 (S15). Thereby, even if the mobile communication terminal is lost, there is no possibility that the presentation information is leaked.

  Subsequently, the control unit 31 operates as the noise image setting unit 312. The noise image setting unit 312 confirms whether an instruction to add the noise image 11 is received from the external device (S16). The instruction to add the noise image 11 is transmitted from the security center server device or the like together with the new noise image 11 and its ID number 40. This additional instruction transmission is performed in conjunction with the separate transmission of the new screen 2. If an addition instruction has been received (YES in S16), the noise image setting means 312 additionally registers the received noise image 11 and its ID number 40 in the storage unit 34 (S17).

  On the other hand, if no additional instruction has been received (NO in S16), noise image setting means 312 skips step S17.

  Next, the noise image setting unit 312 confirms whether an instruction to delete the noise image 11 is received from the external device (S18). An instruction to erase the noise image 11 is transmitted from the server device of the security center together with the ID number 40 of the noise image 11 to be erased. This erasure instruction transmission is performed for all the mobile communication terminals 3 in response to the destruction or loss of the screen 2. If an erasure instruction has been received (YES in S18), noise image setting means 312 erases noise image 11 corresponding to ID number 40 received from storage unit 34 (S19). Since the hidden image 13 using the noise image 11 corresponding to the discarded or lost screen 2 is never projected after the erasure, confidential information is not leaked to the person who finds the screen 2. On the other hand, when no erasure instruction has been received (NO in S18), noise image setting means 312 skips step S19. When the above process is completed, the process returns to S10 to execute the next cycle.

  Next, the operation of the projector 1 will be described.

  The control unit 111 confirms whether the image input unit 110 has received the concealment image 13 from the mobile communication terminal 3. When receiving, the control unit 111 stores the received hidden image 13 in the storage unit 113. The control unit 111 outputs an activation signal to the projection unit 112 to activate the projection unit 112, reads the concealed image 13 from the storage unit 113, and outputs the concealed image 13 to the projection unit 112. The control unit 111 constantly checks the state of the projection stop switch 114, and when a projection stop operation is detected, outputs a stop signal to the projection unit 112 to stop projection.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various deformation | transformation is possible.

  For example, in the present embodiment, as illustrated in FIG. 1, when the hidden information 13 is generated by combining the presentation information image 10 and the noise image 11, the noise image 11 is calculated from the pixel value of each pixel of the presentation information image 10. Subtraction processing for subtracting the pixel value of the corresponding pixel is performed. On the contrary, addition processing for adding the pixel value of the corresponding pixel of the noise image 11 to the pixel value of each pixel of the presentation information image 10 is performed. The concealment image 13 may be generated by In this case, instead of the color adding operation 14 of FIG. 1, it is sufficient to generate a color reducing operation for reducing the noise image 11, and more specifically, an image obtained by inverting the luminance of the noise image 11 may be formed on the surface of the screen. . The present invention converts the presentation information image 10 into an invisible state by using a noise image, and projects the presentation information image 10 in the invisible state onto the screen 2 having the noise image formed on the surface thereof, thereby changing the original presentation information. Although it is restored, it is added that the noise image formed on the surface of the screen 2 includes a noise image obtained by inverting the noise image in which the original presentation information image 10 is not visible. Which noise image is used is determined by a synthesis method.

  In the present embodiment, the noise image 11 in which the pixel value of each pixel is determined by a random number is used. However, the present invention is not limited to this. The noise image 11 may be an image determined according to a predetermined rule such that the presentation information included in the presentation information image 10 becomes invisible when the presentation information image 10 and the noise image 11 are combined. For example, instead of determining the pixel value of each pixel by a random number, the pixel value may be determined so as to have a pattern irrelevant to the presentation information (for example, a sequence of numbers such as 12345...). In this case, when the presentation information image 10 and the noise image 11 are combined, the pixel value of the noise image 11 is determined to be dominant over the pixel value of the presentation information image 10. For example, the pixel value may be determined so that the pixel value of the noise image 11 is lower than the pixel value of the presentation information image 10. Here, in order to make the presentation information included in the presentation information image 10 more difficult to visually recognize, the pixel values of the noise image 11 are not uniform, and the presentation information included in the presentation information image 10 is text information. In some cases, pixel values may be determined so that the noise image 11 has an image pattern finer than the size of the character.

  In the present embodiment, the concealment image 13 transmitted from the mobile communication terminal 3 is stored in the storage unit 113 of the projector 1, and the concealment image 13 stored in the storage unit 113 is read and projected from the projection unit 112. However, the projector 1 does not store the concealment image 13 and may project the concealment image 13 generated by the mobile communication terminal 3 by the projection unit 112 as it is. When the mobile communication terminal 3 and the projector 1 are integrated, the concealed image 13 may be generated, stored, and projected by an integrated projector with a communication function. Further, the projector with the communication function may be configured to store the concealed image 13 generated at the monitoring center in the storage unit and project it on the screen 2 without generating the concealed image 13.

  1 projector, 2 screen, 3 mobile communication terminal, 10 presentation information image, 11 noise image, 13 concealed image, 15 projected image.

Claims (3)

An image projection system comprising a projector and a screen,
A storage unit for storing a noise image determined according to a predetermined rule;
An image generating unit that generates a concealed image by subtracting the noise image from the presentation information image;
A projection unit that projects the concealed image onto a screen on which the noise image is formed, and
An image projection system, wherein the presentation information image is restored on the screen by the projection.   The image projection system according to claim 1, wherein the image generation unit sets a pixel value such that a pixel value of the presentation information image is higher than a pixel value of the noise image. The screen is a glove;
The image projection system according to claim 1, wherein the projector is a projector that can be mounted on a user's body.